Method and arrangement for making and mounting gold crowns,metal bridges and the like



Oct. 21. 1969 G. K. s. KARLSTROM 3.473223 METHOD AND ARRANGEMENT FOR MAKING AND MOUNTING GOLD CROWNS, METAL BRIDGES AND THE LIKE Filed March 6, 196'? 2 Sheets-Sheet 1 PRIOR ART PRIOR ART PRIOR ART PRIOR ART PRIOR ART BY i ATTGEA/YS 0d:- 21. 1969 G. K. s. KARLSTROM 3.4733

METHOD AND ARRANGEMENT FOR MAKING AND MOUNTING GOLD CROWNS, METAL BRIDGES AND THE IJIKE 2 Sheets-Sheet 2 Filed March 6, 1967 INVENTQ'R GOEAA/ K/VZ/T 5/1/1051 KAKZSTEO/f BY 2/4145; $MWZ )f US. Cl. 32-12 3 Claims ABSTRACT OF THE DISCLOSURE A method for locating a crown pin in the crown so that the exposed end of the pin does not abut the bottom surface of a hole drilled in the tooth to receive the pin when the crown is mounted on the tooth. A temporary pin having a relieved portion on the bottom end thereof is initially positioned in the hole in the tooth to permit formation of an impression of the tooth and the formation of a casting of the tooth and pin. The relieved portion of the temporary pin forms an abutment surface in the casting which limits the extent of the crown pin from the crown to an amount less than the depth of the hole in the tooth, when the crown is formed. Thus, the lower end of the crown pin will be free from contact with the bottom surface of the hole when the crown is positioned on the tooth.

It is common practice to secure gold crowns, gold inserts and bridges on teeth by boring a plurality of parallel holes in the teeth and providing the gold crown with a number of metal pins, disposed parallel with one another, and passing said pins into the corresponding holes in the tooth and anchoring them therein by means of a dental cement. It has shown in practice that the pins in gold crowns mounted in this way are liable to cause irritation of the tooth pulp, due to thermal effects, subjecting the patient to some discomfort. In order to illustrate clearly the problem which the present invention is intended to solve, a known method will be described with reference to accompanying drawings, FIGS. 15. These figures show the various steps in the manufacture of a gold crown and in how a tooth is capped with the same.

Shown in perspective in FIG. 1 is a tooth 1, the upper surface 2 of which has been ground fiat. Disposed in the longitudinal direction of the tooth are four holes 3, drilled parallel with one another and each extending substantially the same distance into the tooth. Plastic pins 4 are inserted in the holes 3, the pins projecting above the surface 2 and being provided at the top with a head 5 which assists in anchoring the tooth in an impressionmass 6 contained in a box 7, or some other suitable container, which is passed down over the tooth. When the box 7 together with the mass 6 is pressed down over the tooth, an impression of the tooth, together with the pins 4, 5, is obtained in the said mass.

FIG. 2 shows the mass 6 and the box 7 placed in a mold 8, the mass presenting a cavity or impression 9 caused by the tooth 1 and corresponding to its shape. The ends of the pins 4, i.e. the ends which were previously inserted in the holes 3 in the tooth 1, project up out of the impression 9. Gypsum is now poured into the mold 8 and allowed to solidify, a cast of the tooth proper being obtained.

The cast 10 is shown in FIG. 3 and is provided with holes 11 which correspond to the holes 3 in tooth 1. Metal pins 12 are inserted into the holes 11, whereupon gold is molded over the cast tooth 10 so that the metal pins 12 are grouted in the prospective gold crown 13.

nited States Patent 0 FIG. 4 shows, in section, the position of the metal pins 12 in the holes 11 in the gipsum impression 10, and the position of the gold crown 13 above the said plaster impression. When all work on the gold crown has been completed, the plaster impression 10 is removed so that only the said gold crown 13, together with the pins 12, remains.

The unit obtained thus is now inserted into the tooth 1, the pins 12 being passed into the holes 3 in the tooth (FIG. 5). Before passing the pins 12 down in the holes 3 a layer of cement is, of course, applied to the upper surface 2 of the tooth and in the holes 3. When the pins and the gold crown have been passed down into position, the pins abut the bottom of the holes 3 to a certain extent, and thus if the fit is correct the bottom of the gold crown 14 ideally lies against the surface 2. However, in practice this ideal is not always achieved since the pins 12 are prevented from penetrating down to the bottom of the hole owing to compacting of the dental cement. The pins 12 namely displace a certain amount of cement during their passage in the holes 3, which compacts and prevents the pins from reaching the desired bottom position. As a result of this a clearance 15 is left between the gold crown and the surface 2 of the tooth. This clearance is naturally filled with cement but, neverthe less, is not desirable. It is also possible that errosions take place in time within the cement filling, possibly causing cavities. A further disadvantage with this method is that the pins 12, if the method succeeds with respect to the ideal disclosed above, abut the bottom of the holes 3, which is not to advantage since the pulp of the tooth can be afiected by heat and pressure, causing irritation and thus discomfort.

The present invention is intended to circumvent these disadvantages by providing for tight abutment of the gold crown or the like against the tooth whilst at the same time also providing for attachment of the crown, which is as equally secure as in earlier methods, and reducing the effects of the thermal irritations on the pulp of the tooth.

The present invention fulfils its object by means of the characterizing features disclosed in the claims.

An embodiment of the invention will be described below with reference to FIGS. 69 which show diagrammatically, and in section, various steps taken in the manufacture of a gold crown whilst adopting the method according to the present invention.

FIG. 6 shows in enlarged scale and in section the tooth 1, as in FIG. 1, at a hole 3 in which a plastic pin 16 has been inserted. The lower end surface 17 of the plastic pin is flat but has a point 18 projecting centrally away from the same, the point abutting the central V- shaped bottom portion of the hole 3. As can be seen from the drawing the end surface 17 is situated at a certain level above the lowermost cylindrical portion of the hole, i.e. above the demarcation line between the cylindrical wall surface and the conical bottom surface. The pin 16 is provided at the top with a conical head piece 19 the shape of which is such that the impression mass 20, which is to be passed down over the pin and the tooth, can slide easily around the headpiece 19 of the pin, and the pin may more easily penetrate the impression mass at the same time as it is anchored in the impression mass, just as stably as was the case with the pin 4 and the head 5 in FIG. 1.

Subequent to forcing the impression mass 20 down over the pins and tooth, as in FIG. 1, a cavity is obtained in the impression mass, as in FIG. 2, which is filled with gypsum. FIG. 7 shows the pin 16 in the impression mass 20, grouted in gypsum 21.

When the gypsum 20 has solidified a cast of the tooth is obtained, as in FIG. 3. A section of a cast of the pin 16 and a portion of the tooth is shown in FIG. 8. A hole 22 corresponding to the free end of the pin 16 is thus obtained in the plaster and a bottom abutment surface 23 corresponding to the end surface 17 of the pin 16 is obtained together with a recess 24 corresponding to the point 18, the lowermost point of the recess 24 corresponding to the lowermost point of the bottom surface of the drilled hole 3 formed within the tooth 1. The gypsum material surrounding the recess 24, as defined by the upper abutment surface 23, thus substantially functions as an abutment member which is formed due to the relieved portion or different crosssectional configuration of the pin 16 at the lower end thereof, which lower end is formed as the conical point 18 in the embodiment illustrated in FIGURES 69. A metal pin 25 is then inserted -in the hole 22, until the end surface thereof contacts the abutment surface 23, whereupon gold 26 is applied to the upper surface of the plaster, whereby the metal pin becomes anchored in the gold 26. After the gold crown 26 has been formed, the metal crown pin 25 thus extends therefrom a distance which is less than the depth of the hole 3 drilled in the tooth 1.

When all work to the gold crown has been completed, the crown is moved over to the tooth 1 (FIG. 9), the hole 3 and the upper surface 2 being filled with cement 27 as before. When the pin 25 has been passed down into the hole 3 the cement 27 is pressed up along the sides of the hole and the cement present on the upper surface 2 of the tooth is forced out so that only a very thin layer remains. As can be seen from the drawings when the bottom surface of the gold crown comes into contact with the ground upper surface 2 of the tooth the lower end surface of the pin 25 no longer abuts the bottom of the hole 3 but remains some small distance away from the same. In this way it is ensured that an absolute uniform abutment is obtained between the gold crown and the upper surface of the tooth at the same time as the pin no longer abuts the tooth proper but merely comprises an anchorage in the same. Because of the arrangement of the point 18 the bottom surface 23 in the plaster cast 21 will not, in actual fact, completely correspond to the bottom surface of the hole, in the tooth. It should also be observed that the pin 25 'has a somewhat smaller outer diameter than the diameter of the hole 3 in the tooth, to allow the cement to flow up along the outer surface of the pin.

As can be seen the present invention, by means of a simple arrangement provides for considerable improvement with respect to the task of fitting teeth with gold crowns, dental bridges, etc. The invention isnaturally not restricted to the described embodiment of the pin, either the pins which are first inserted in the hole for making a cast or the tooth of the metal pins which are secured together with the crown or bridge.

What is claimed is: 1. A method of making a tooth crown and of mounting same on a tooth, comprising the steps of:

providing in said tooth a first hole having a determined depth as defined by the bottom surface of said hole;

making a model of said tooth, said model having the external configuration of at least the upper part of said tooth and said model containing a second hole corresponding to said first hole, said second hole having a depth substantially equal to the depth of said first hole and including an abutment member in the lower end of the second hole forming an abutment surface in said model which is spaced upwardly from the bottom surface of said second hole;

positioning a crown pin within said second hole with the lower end of said crown pin being positioned in contact with said abutment surface, the upper end of said crown pin projecting outwardly from said model;

forming a crown adjacent to at least the upper part or said model with said crown surrounding the projecting upper end of said crown pin;

removing said crown from said model with the lower end of said crown pin projecting from said crown: and

positioning said crown on said tooth with the projecting portion of said crown pin being inserted into said first hole whereby the lower end of the crown pin is free of contact with the bottom surface of said first hole.

2. A method according to claim 1, further including the steps of:

positioning a temporary pin within said first hole or said tooth with the lower end of said temporary pin abutting the bottom surface of said first hole, the upper end of said temporary pin projecting outwardly from said tooth, the lower end of said temporary pin further having recess means defining a limit surface spaced upwardly from the bottom surface of said first hole;

positioning a mass of impressionable material over said tooth with the projecting upper end of said temporary pin extending into said mass; removing said mass from said tooth to provide an impression therein corresponding to the configuration of said tooth, the upper end of said temporary pin being embedded in said mass and the lower end of said temporary pin extending into said impression; filling said impression with a suitable material for making a cast model corresponding to the configuration of said tooth, said material surrounding the projecting lower end of said temporary pin to form in said cast model said second hole, said second hole having a depth corresponding to the depth of the first hole formed in said tooth, said material further filling in the recess means formed in the lower end of said temporary pin to form an abutment means having an abutment surface spaced from the bottom surface of said second hole;

said cast model with said second hole formed therein then being removed from said mass of impressionable material with said crown pin then being inserted into said second hole to permit formation of sand crown around the projecting upper end of said crown pin, the lower end of said crown pin abutting against the abutment surface and being spaced from the bottom surface of said second hole.

3. A method according to claim 2, wherein the temporary pin has a cylindrical outer surface substantially corresponding to the diameter of the hole formed in the tooth, the lower end of said temporary pin having an axially extending portion of reduced cross-sectional area with the lower end of said portion being adapted to abut against the bottom surface of said first hole when said temporary pin is inserted in said tooth, the other end of said portion defining said limit surface spaced upwardly a small distance from the bottom surface or said first hole.

References Cited FOREIGN PATENTS 5/1963 France. 8/1933 Great Britain.

OTHER REFERENCES ROBERT PESHOCK, Primary Examiner 

